A reactive power control method and system for flexible direct current transmission

Abstract

The present application discloses a reactive power control method and system for flexible direct current (DC) transmission, belonging to the technical field of flexible DC transmission. The present application fully utilizes the reactive power capability of the flexible DC transmission system itself, outputs different reactive inner loop currents or reactive power instructions by judging the reactive control working mode, and realizes automatic control of the reactive power and voltage of the power grid, thereby avoiding frequent manual adjustment of reactive power by operators. The flexible DC transmission system utilizes the reactive power rapid response capability to rapidly adjust the AC voltage when the AC voltage is abnormal. At the same time, the flexible DC transmission system exchanges information with the reactive power control device of the power grid. The reactive power control device of the power grid inputs corresponding reactive capacitors and reactors according to the exchanged information, and replaces the additional reactive power output by the flexible DC transmission system, thereby meeting the dual requirements of steady-state reactive power control and fault reactive power control.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible direct current transmission, and in particular relates to a reactive power control method and system for flexible direct current transmission. Background Art

[0002] Flexible DC transmission systems offer flexible control, rapid dynamic response, and low harmonic content. They can quickly and independently adjust active and reactive power, and have broad application prospects. Especially in the field of reactive power control, their fast response allows them to quickly provide reactive power during AC system fault and recovery phases, supporting grid voltage during faults and accelerating voltage recovery. During steady-state operation, they can also provide reactive power according to system requirements to regulate steady-state voltage.

[0003] After the flexible DC transmission system is connected to the AC system, the AC voltage changes frequently due to changes in the AC system's load. In particular, when the AC voltage fails to meet the voltage range requirements of the superior dispatcher, the operating personnel need to manually adjust the reactive power frequently. Therefore, the flexible DC transmission system needs to be able to automatically adjust the voltage after the AC voltage exceeds the range to bring the voltage back into the normal range. However, since the reactive power output of the automatic voltage regulation after the AC voltage exceeds the range is too large, it consumes the flexible DC system's own reactive power reserves, thereby affecting the effectiveness of the reactive power support voltage during faults. The existing solution cannot meet the dual needs of steady-state reactive power control and fault reactive power control. Summary of the Invention

[0004] The technical problem to be solved by the present application is to overcome the defects of the above-mentioned existing technologies and provide a reactive power control method and system for flexible direct current transmission. By judging the reactive power control working mode, different reactive inner loop currents or reactive power instructions are output to realize automatic control of reactive power and voltage. At the same time, by exchanging information with the reactive power control system of the power grid, the flexible direct current reactive power is coordinated with the reactive reactors and capacitors of the power grid, thereby meeting the dual needs of steady-state reactive power control and fault reactive power control.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted in this application is as follows.

[0006] The present application provides a reactive power control method for flexible direct current transmission, comprising the following steps:

[0007] Detect system runtime data;

[0008] Determine the working mode of reactive power control based on the detected data;

[0009] Output reactive power instruction and execute the instruction according to the judgment result of working mode;

[0010] Synchronously transmit the judgment result of the working mode and the reactive power instruction to the reactive power control device of the power grid;

[0011] The power grid reactive power control device performs reactive power control in response to the reactive power control instruction.

[0012] In some embodiments, the operating modes include an abnormally low voltage operating mode, a normal operating mode, an abnormally high voltage operating mode, a first low voltage ride through operating mode, a second low voltage ride through operating mode, and a high voltage ride through operating mode.

[0013] In some embodiments, when U m Meet U m ≤k L2 U N When , the reactive power control is in the second low voltage ride-through working mode;

[0014] WhenU m Satisfy k L2 U N m ≤k L1 U N When , the reactive power control is in the first low voltage ride-through working mode;

[0015] When U m Satisfy k L1 U N m ≤k L U N When , the reactive power control is in the abnormally low voltage working mode;

[0016] When U m Satisfy k L U N m <k H U N When , the reactive power control is in the normal working mode;

[0017] When U m Satisfy k H U N ≤U m <k H1 U N When , the reactive power control is in the abnormally high voltage working mode;

[0018] WhenU m Satisfy k H1 U N ≤U m When , the reactive power control is in the high voltage ride through working mode;

[0019] Among them, U m ​​​is the amplitude of the positive sequence component of the AC system voltage, U N is the rated value of the positive sequence component of the AC system voltage, k L ,k L1 ,k L2 ,k H ,k H1 Are all voltage coefficients and satisfy the relationship: 0 <k L2 <k L1 <k L <1 <k H <k H1 .

[0020] In some embodiments, when the reactive power control is in the second low voltage ride-through mode, its reactive current inner loop reference instruction i qref =0 or i qref =k LF2 ; where k LF2 The reactive current reference command setting value in the second low voltage ride-through mode satisfies: 0≤k LF2 ≤1p.u.;

[0021] When the reactive power control is in the first low voltage ride-through mode, its reactive current inner loop reference instruction i qref =k LF1 , where k LF1 =G LF1 (U N -U m ), G LF1 A proportional-integral controller for a first low voltage ride-through operating mode;

[0022] When the reactive power control is in abnormal low voltage working mode, its reactive power control reference instruction Q ref =Q ord +Q L , where Q ord The reactive power command input to the system, Q L It is the additional reactive power instruction in abnormal low voltage working mode, Q L =G L (k L U N -U m ), G L Proportional-integral controller for abnormally low voltage operation mode;

[0023] When the reactive power control is in normal working mode, its reactive power control reference instruction Q ref =Q ord ;

[0024] When the reactive power control is in abnormal high voltage working mode, its reactive power control reference instruction Q ref =Q ord+Q H , where Q H It is the additional reactive power instruction in abnormally high voltage working mode, Q H =G H (k H U N -U m ), G H Proportional-integral controller for abnormally high voltage operation mode;

[0025] When the reactive power control is in the high voltage ride-through mode, the reactive current inner loop reference instruction i qref =k HF1 , where k HF1 =G HF1 (U N -U m ), G HF1 It is a proportional-integral controller for high voltage ride-through mode.

[0026] In some embodiments, when the reactive power control is in the first low voltage ride-through mode, 0≤k LF1 =G LF1 (U N -U m )≤I qL1set , I qL1set It is the reactive current reference value set according to the system voltage.

[0027] In some embodiments, the input reactive power command Q ord Satisfaction: Q min ≤Q ord ≤Q max , reactive power control reference instruction Q ref Satisfaction: Q min ≤Q ref ≤Q max , Q min ,Q max are the minimum and maximum reactive power values ​​calculated based on the system.

[0028] In some embodiments, when the reactive power control is in the high voltage ride through mode, I qHset ≤k HF1 =G HF1 (U N -U m )≤0,I qHset It is the reactive current reference value set according to the system voltage.

[0029] The present application also provides a reactive power control system for flexible direct current transmission, which is applied to the reactive power control method for flexible direct current transmission as described in any of the aforementioned embodiments. The reactive power control system includes: a flexible direct current transmission reactive power control device and a power grid reactive power control device electrically connected;

[0030] The flexible direct current transmission reactive power control device comprises:

[0031] The reactive working mode judgment module is used to judge the working mode of the reactive control according to the detected data and obtain the result of the working mode judgment;

[0032] A reactive instruction output module is used to output a reactive current inner loop reference instruction or a reactive control reference instruction or an additional reactive instruction for an abnormally low voltage working mode or an additional reactive instruction for an abnormally high voltage working mode according to the result of the reactive working mode judgment module;

[0033] A reactive communication module, configured to transmit the results of the reactive working mode determination module and the reactive instruction output module to the grid reactive control device, and simultaneously receive reactive control instructions issued by the grid reactive control device;

[0034] a reactive power execution module, configured to execute a reactive power instruction using the result of the reactive power instruction output module as a reference value;

[0035] The grid reactive power control device activates the corresponding reactive reactor or capacitor according to the communication data transmitted by the reactive communication module: the additional reactive power instruction of the abnormally low voltage working mode or the additional reactive power instruction of the abnormally high voltage working mode.

[0036] In some embodiments, the communication content between the reactive communication module and the grid reactive control device further includes: the operation mode of the flexible direct current transmission system, the reactive limit value, the unlocking state and the reactive control mode.

[0037] In some embodiments, the period in which the grid reactive power control device switches reactive capacitors or reactors on or off is greater than or equal to the reactive power execution time of the flexible direct current transmission system.

[0038] In some embodiments, the grid reactive power control device sends a reactive power command value to the flexible DC transmission reactive power control device, and the reactive power command value is used as the reactive power command Q input by the system. ord .

[0039] Compared with the prior art, this application has the following beneficial effects:

[0040] The present invention relates to a reactive power control method for flexible direct current transmission, comprising the following steps: detecting data during system operation; determining the working mode of reactive power control based on the detected data; outputting a reactive power instruction based on the determination result of the working mode; transmitting the determination result of the working mode and the reactive power instruction to a power grid reactive power control device; and the power grid reactive power control device correspondingly issuing the reactive power control instruction to perform reactive power control. The present invention fully utilizes the reactive power capability of the flexible direct current transmission system itself, outputs different reactive inner loop currents or reactive power instructions by determining the reactive power control working mode, and realizes automatic control of the reactive power and voltage of the power grid, thereby avoiding the operator from manually and frequently adjusting the reactive power in steady state; utilizes the reactive power fast response capability of the flexible direct current transmission system, and quickly adjusts the AC voltage when the AC voltage is abnormal. At the same time, the flexible direct current transmission system exchanges information with the power grid reactive power control device, and the power grid reactive power control device, based on the exchanged information, inputs corresponding reactive capacitors and reactors to replace the additional reactive power output by the flexible direct current transmission system, thereby meeting the dual requirements of steady-state reactive power control and fault reactive power control.

[0041] An embodiment of the present application also provides a reactive power control system for flexible direct current transmission, which is applied to the control method as described above. It can be understood that the reactive power control system can realize the functions of the reactive power control method and thus has the same beneficial effects as the reactive power control method, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 This is a flow chart of a reactive power control method for flexible direct current transmission of the present application;

[0044] Figure 2 is a schematic diagram of the abnormally low voltage operating mode, normal operating mode, and abnormally high voltage operating mode of the present application;

[0045] Figure 3 Schematic diagram of the first low voltage ride-through operating mode, the second low voltage ride-through operating mode, and the high voltage ride-through operating mode of the present application;

[0046] Figure 4 This is a reactive instruction block diagram of the flexible DC transmission reactive control device of the present application;

[0047] Figure 5 This is a schematic diagram of the device composition of the reactive power control system of the flexible direct current transmission of the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, in the description of the present application, the term "including" means "including but not limited to". In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0049] The applicant noted that after the flexible DC transmission system is connected to the AC system, the AC voltage changes frequently due to changes in the load of the AC system, especially when the AC voltage fails to meet the voltage range requirements of the superior dispatcher, which causes the operating personnel to manually adjust the reactive power frequently. Therefore, the flexible DC transmission system needs to be able to automatically adjust the voltage after the AC voltage exceeds the range to bring the voltage back to the normal range; however, since the reactive power output of the automatic voltage regulation after the AC voltage exceeds the range is too large, the reserve reactive power of the flexible DC system itself is consumed, thereby affecting the effect of reactive support voltage during faults. The existing solution cannot meet the dual needs of steady-state reactive power control and fault reactive power control.

[0050] In view of this, the present application provides a reactive power control method and system for flexible direct current transmission, which can coordinate reactive voltage, avoid operators from frequently manually adjusting reactive power, and meet the dual needs of steady-state reactive power control and fault reactive power control.

[0051] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments.

[0052] Please refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 An embodiment of the present application provides a reactive power control method for flexible direct current transmission, comprising the following steps:

[0053] S1: Data when the detection system is running.

[0054] Specifically, it refers to detecting the voltage positive sequence component amplitude U of the AC system m .

[0055] S2: Determine the working mode of reactive power control based on the detected data.

[0056] Specifically, according to the detection of the positive sequence component amplitude U of the AC system voltage mDifferent reactive power control operating modes can be classified based on the differences in voltage. The corresponding reactive power control operating modes include: abnormally low voltage operating mode, normal operating mode, abnormally high voltage operating mode, first low voltage ride-through operating mode, second low voltage ride-through operating mode, and high voltage ride-through operating mode. The control method of this application provides corresponding judgment conditions for each of these different reactive power control operating modes, as follows.

[0057] WhenU m Meet U m ≤k L2 U N When the reactive power control is in Figure 3 The second low voltage ride-through operating mode is shown.

[0058] WhenU m Satisfy k L2 U N m ≤k L1 U N When the reactive power control is in Figure 3 The first low voltage ride-through operating mode is shown.

[0059] WhenU m Satisfy k L1 U N m ≤k L U N When the reactive power control is in Figure 2 Abnormally low voltage operating mode shown.

[0060] WhenU m Satisfy k L U N m <k H U N When , reactive power control is in normal working mode.

[0061] WhenU m Satisfy k H U N ≤U m <k H1 U N When , the reactive power control is in abnormally high voltage working mode.

[0062] WhenU m Satisfy k H1 U N ≤U m When the reactive power control is in Figure 3 The high voltage ride through mode is shown.

[0063] Among them, U m ​​​is the amplitude of the positive sequence component of the AC system voltage, U N is the rated value of the positive sequence component of the AC system voltage, k L ,k L1 ,k L2 ,k H ,k H1 Are all voltage coefficients and satisfy the relationship: 0 <k L2 <k L1 <k L <1 <k H <k H1 .

[0064] S3: Output reactive power instruction according to the judgment result of the working mode and execute the instruction.

[0065] According to the judgment result of the above working mode, the reactive inner loop current or reactive command required for reactive power control is output accordingly.

[0066] Specifically, when the reactive power control is in the second low voltage ride-through mode, its reactive current inner loop reference instruction i qref =0 or i qref =k LF2 ; where k LF2 The reactive current reference command setting value in the second low voltage ride-through mode satisfies: 0≤k LF2 ≤1p.u..

[0067] When the reactive power control is in the first low voltage ride-through mode, its reactive current inner loop reference instruction i qref =k LF1 , where k LF1 =G LF1 (U N -U m ), G LF1 It is a proportional-integral controller in the first low voltage ride-through mode.

[0068] Furthermore, when the reactive power control is in the first low voltage ride-through mode, 0≤k LF1 =G LF1 (U N -U m )≤I qL1set , where I qL1set It is the reactive current reference value set according to the system voltage.

[0069] When the reactive power control is in abnormal low voltage working mode, its reactive power control reference instruction Q ref =Q ord +Q L ,like Figure 4 As shown, where Q ord The reactive power command input to the system, QL It is the additional reactive power instruction in abnormal low voltage working mode, Q L =G L (k L U N -U m ), G L It is a proportional-integral controller for abnormal low voltage operation mode.

[0070] Further, such as Figure 4 As shown, the input reactive power instruction Q ord Satisfaction: Q min ≤Q ord ≤Q max , reactive power control reference instruction Q ref Satisfaction: Q min ≤Q ref ≤Q max , where Q min ,Q max are the minimum and maximum reactive power values ​​calculated based on the system.

[0071] When the reactive power control is in normal working mode, its reactive power control reference instruction Q ref =Q ord .

[0072] When the reactive power control is in abnormally high voltage working mode, its reactive power control reference instruction Q ref =Q ord +Q H ,like Figure 4 As shown, where Q H It is the additional reactive power instruction in abnormally high voltage working mode, Q H =G H (k H U N -U m ), G H It is a proportional-integral controller for abnormally high voltage operation mode.

[0073] When the reactive power control is in the high voltage ride-through mode, the reactive current inner loop reference instruction i qref =k HF1 , where k HF1 =G HF1 (U N -U m ), G HF1 It is a proportional-integral controller for high voltage ride-through mode.

[0074] Furthermore, when the reactive power control is in the high voltage ride-through mode, I qHset ≤k HF1 =G HF1 (U N-U m )≤0, where I qHset It is the reactive current reference value set according to the system voltage.

[0075] S4: Synchronously transmit the judgment result of the working mode and the reactive power instruction to the grid reactive power control device.

[0076] S5: The grid reactive power control device performs reactive power control in response to the reactive power control instruction.

[0077] This application utilizes a flexible direct current transmission reactive power control device to determine the operating mode of reactive power control and output a reactive power instruction based on the operating mode. Simultaneously, the flexible direct current transmission system executes the reactive power instruction and outputs reactive power. The reactive power control device then synchronously transmits the reactive power control mode determination result and the reactive power instruction to the grid reactive power control device. The grid reactive power control device then issues the corresponding reactive power control instruction and replaces the reactive power with reactive capacitors and reactors, thereby achieving online automatic control of reactive power and voltage. This avoids the need for operators to frequently and manually adjust reactive power during steady-state operation, effectively freeing up manpower while also supporting system voltage and rapidly recovering voltage in the event of a fault.

[0078] It should be noted that this application detects the amplitude of the positive-sequence component of the AC system voltage and divides the reactive control working mode according to the rated value of the positive-sequence component of the AC system voltage and the corresponding voltage coefficient. The measurement data is small and the calculation involved is simple, avoiding complicated data measurement and complex calculations.

[0079] The present application also provides a flexible direct current transmission reactive power control system, which is applied to the flexible direct current transmission reactive power control method as described in any of the above embodiments. The reactive power control system includes: a flexible direct current transmission reactive power control device and a power grid reactive power control device electrically connected;

[0080] The flexible direct current transmission reactive power control device comprises:

[0081] The reactive working mode judgment module is used to judge the working mode of the reactive control according to the detected data and obtain the result of the working mode judgment;

[0082] A reactive instruction output module is used to output a reactive current inner loop reference instruction or a reactive control reference instruction or an additional reactive instruction for an abnormally low voltage working mode or an additional reactive instruction for an abnormally high voltage working mode according to the result of the reactive working mode judgment module;

[0083] A reactive communication module, configured to transmit the results of the reactive working mode determination module and the reactive instruction output module to the grid reactive control device, and simultaneously receive reactive control instructions issued by the grid reactive control device;

[0084] a reactive power execution module, configured to execute a reactive power instruction using the result of the reactive power instruction output module as a reference value;

[0085] The grid reactive power control device activates the corresponding reactive reactor or capacitor according to the communication data transmitted by the reactive communication module: the additional reactive power instruction of the abnormally low voltage working mode or the additional reactive power instruction of the abnormally high voltage working mode.

[0086] In some embodiments, the communication content between the reactive communication module and the grid reactive control device further includes: the operation mode of the flexible direct current transmission system, the reactive limit value, the unlocking state and the reactive control mode.

[0087] The Flexible DC transmission system transmits these communication contents to the grid reactive power control device through the reactive power communication module, so that the grid reactive power control device can monitor the working status of the Flexible DC transmission system in real time, and then can promptly and reliably control the Flexible DC transmission system.

[0088] In some embodiments, the period in which the grid reactive power control device switches reactive capacitors or reactors on or off is greater than or equal to the reactive power execution time of the flexible direct current transmission system.

[0089] It should be noted that the grid reactive power control device in this application activates the corresponding reactive power reactor or capacitor based on the communication data transmitted by the reactive power communication module: the additional reactive power instruction for the abnormally low voltage operating mode or the additional reactive power instruction for the abnormally high voltage operating mode. The purpose is to replace the additional reactive power output by the flexible direct current transmission system, thereby meeting the dual requirements of steady-state reactive power control and fault reactive power control. At this time, it is ensured that the cycle of activation or removal of the reactive capacitor or reactor is greater than or equal to the reactive power execution time of the flexible direct current transmission system, ensuring that the reactive capacitor or reactor can fully complete the replacement of the additional reactive power output by the flexible direct current transmission system, thereby ensuring the system's steady-state reactive power control and fault reactive power control.

[0090] In some embodiments, the grid reactive power control device may send a reactive power command value to the flexible DC transmission reactive power control device, and the reactive power command value may be used as the reactive power command Q input by the system. ord This configuration eliminates the need to set up a control unit in the flexible DC transmission reactive power control device or the flexible DC transmission system to control the system to input reactive power instructions.

[0091] In summary, the reactive power control method and system of flexible direct current transmission in the present application fully utilize the reactive power of the flexible direct current transmission system itself, output different reactive inner loop currents or reactive power instructions by judging the reactive control working mode, and realize automatic control of the reactive power and voltage of the power grid, thereby avoiding the operator's frequent manual adjustment of reactive power in steady state; utilizing the flexible direct current transmission system's ability to quickly respond to reactive power, the AC voltage is quickly adjusted when the AC voltage is abnormal. At the same time, information is exchanged with the grid reactive power control device. The grid reactive power control device inputs corresponding reactive capacitors and reactors according to the exchanged information to replace the additional reactive power output by the flexible direct current transmission system, thereby meeting the dual needs of steady-state reactive power control and fault reactive power control.

[0092] The above embodiments are merely illustrative of the technical concept of the present application and are not intended to limit the scope of protection of the present application. Persons skilled in the art should understand that any modification or equivalent substitution of the specific embodiments of the present application without departing from the technical concept and scope of the present application shall be encompassed by the claims of the present application.

Claims

1. A reactive power control method for flexible direct current transmission, characterized by: The steps include: Detect system runtime data; Determine the working mode of reactive power control according to the detected data; the working modes include abnormally low voltage working mode, normal working mode, abnormally high voltage working mode, first low voltage ride-through working mode, second low voltage ride-through working mode and high voltage ride-through working mode; Output reactive power instruction and execute the instruction according to the judgment result of working mode: When the reactive power control is in the second low voltage ride-through mode, its reactive current inner loop reference instruction i qref =0 or i qref =k LF2 ; where k LF2 The reactive current reference command setting value in the second low voltage ride-through mode satisfies: 0≤k LF2 ≤1p.u.; When the reactive power control is in the first low voltage ride-through mode, its reactive current inner loop reference instruction i qref =k LF1 , where k LF1 =G LF1 (U N -U m ), G LF1 A proportional-integral controller for a first low voltage ride-through operating mode; When the reactive power control is in abnormal low voltage working mode, its reactive power control reference instruction Q ref =Q ord +Q L , where Q ord The reactive power command input to the system, Q L It is the additional reactive power instruction in abnormal low voltage working mode, Q L =G L (k L U N -U m ), G L Proportional-integral controller for abnormally low voltage operation mode; When the reactive power control is in normal working mode, its reactive power control reference instruction Q ref =Q ord ; When the reactive power control is in abnormal high voltage working mode, its reactive power control reference instruction Q ref =Q ord +Q H , where Q H It is the additional reactive power instruction in abnormally high voltage working mode, Q H =G H (k H U N -U m ), G H Proportional-integral controller for abnormally high voltage operation mode; When the reactive power control is in the high voltage ride-through mode, the reactive current inner loop reference instruction i qref =k HF1 , where k HF1 =G HF1 (U N -U m ), G HF1 Proportional-integral controller for high voltage ride-through mode; Among them, U m is the amplitude of the positive sequence component of the AC system voltage, U N is the rated value of the positive sequence component of the AC system voltage, k L ,k H Are all voltage coefficients and satisfy the relationship: 0 <k L <1 <k H ; Synchronously transmit the judgment result of the working mode and the reactive power instruction to the reactive power control device of the power grid; The power grid reactive power control device performs reactive power control in response to the reactive power control instruction.

2. The reactive power control method for flexible direct current transmission according to claim 1, characterized in that: WhenU m Meet U m ≤k L2 U N When , the reactive power control is in the second low voltage ride-through working mode; WhenU m Satisfy k L2 U N m ≤k L1 U N When , the reactive power control is in the first low voltage ride-through working mode;​ WhenU m Satisfy k L1 U N m ≤k L U N When , the reactive power control is in the abnormally low voltage working mode;​ WhenU m Satisfy k L U N m <k H U N When , the reactive power control is in the normal working mode;​ WhenU m Satisfy k H U N ≤U m <k H1 U N When , the reactive power control is in the abnormally high voltage working mode; WhenU m Satisfy k H1 U N ≤U m When the reactive power control is in the high voltage ride-through mode, k L1 ,k L2 ,k H1 Are all voltage coefficients and satisfy the relationship: 0 <k L2 <k L1 <k L <1 <k H <k H1 .

3. The reactive power control method for flexible direct current transmission according to claim 1, characterized in that: When the reactive power control is in the first low voltage ride-through mode, 0≤k LF1 =G LF1 (U N -U m )≤I qL1set , I qL1set It is the reactive current reference value set according to the system voltage.

4. The reactive power control method for flexible direct current transmission according to claim 1, characterized in that: Input reactive power command Q ord Satisfaction: Q min ≤Q ord ≤Q max , reactive power control reference instruction Q ref Satisfaction: Q min ≤Q ref ≤Q max , Q min ,Q max are the minimum and maximum reactive power values ​​calculated based on the system.

5. The reactive power control method for flexible direct current transmission according to claim 1, characterized in that: When the reactive power control is in the high voltage ride-through mode, I qHset ≤k HF1 =G HF1 (U N -U m )≤0,I qHset It is the reactive current reference value set according to the system voltage.

6. A reactive power control system for flexible direct current transmission, characterized by: The reactive power control method for flexible direct current transmission according to any one of claims 1 to 5, wherein the reactive power control system comprises: a flexible direct current transmission reactive power control device and a grid reactive power control device electrically connected; The flexible direct current transmission reactive power control device comprises: The reactive working mode judgment module is used to judge the working mode of the reactive control according to the detected data and obtain the result of the working mode judgment; A reactive instruction output module is used to output a reactive current inner loop reference instruction or a reactive control reference instruction or an additional reactive instruction for an abnormally low voltage working mode or an additional reactive instruction for an abnormally high voltage working mode according to the result of the reactive working mode judgment module; A reactive communication module, configured to transmit the results of the reactive working mode determination module and the reactive instruction output module to the grid reactive control device, and simultaneously receive reactive control instructions issued by the grid reactive control device; a reactive power execution module, configured to execute a reactive power instruction using the result of the reactive power instruction output module as a reference value; The grid reactive power control device activates the corresponding reactive reactor or capacitor according to the communication data transmitted by the reactive communication module: the additional reactive power instruction of the abnormally low voltage working mode or the additional reactive power instruction of the abnormally high voltage working mode.

7. The reactive power control system for flexible direct current transmission according to claim 6, characterized in that: The communication content between the reactive communication module and the grid reactive control device also includes: the operation mode of the flexible direct current transmission system, the reactive limit value, the unlocking state and the reactive control mode.

8. The reactive power control system for flexible direct current transmission according to claim 6, characterized in that: The period in which the grid reactive power control device switches on or off reactive capacitors or reactors is greater than or equal to the reactive power execution time of the flexible direct current transmission system.

9. The reactive power control system for flexible direct current transmission according to claim 6, characterized in that: The grid reactive power control device sends a reactive power command value to the flexible DC transmission reactive power control device, and the reactive power command value is used as the reactive power command Q input by the system. ord .

Images